asterisk users - Jan 2004 - Asterisk stops responding after about 80 calls

Hello all,

We are having a really wierd problem with asterisk, basically after
about 80 calls, asterisk stops responding.  The process itself is still
running, you can log into asterisk and events are still logged, however
all phones lose dial tone and no incoming or outgoing calls work.

Calls come in over a ISDN PRI line and are routed over IAX to another
asterisk server that has an Adtran channel bank connecting 24 phones. 
Both servers have a TE410P digium card in them.

The system was actually running fine for several weeks without any
problem, however we switched to a different PRI and since then this
problem has been appearing.  The box that the problem happens on is the
one with the channel bank connected to it, the box with the PRI runs
perfectly.

We have essentially tried everything but to no avail.  Our hope is that
someone can some information that can help.

For the record, we are running a CVS version that is about 3 weeks - 1
month old, however we did upgrade to today's CVS and that did not fix
anything.  We have also tried all types of signalling for our channel
bank connection, including kewlstart, loopstart, and groundstart.

Any help would be greatly appreciated.  We would also like to put out a
call to any consultants who can help as we would be willing to pay an
asterisk expert who wants to give us some of their time on this problem.

Thanks,
Derek